Ostracods as model species to detect the effects of endocrine disruptors compounds from surface and groundwater

Ostracods are tiny crustaceans that live inmost aquatic habitats in all marine and freshwater ecoregions of the world. Their body is protected and completely enclosed by shell formed by two (often strongly calcified) valves, and that is why they are sometimes known as seed shrimps or mussel shrimps.

Ostracods plates
Electronic microscopy images of ostracods carapaces

Non-marine species, usually less than 2 mm in size, are essentially benthic or nektobenthic and can be found in a variety of habitats from watering troughs for domestic livestock, pails and other artificial structures, through all kinds of natural permanent and temporary surface waters and various ground waters to thermal springs with water temperature reaching 50°C, damp moss and rainforest leaf litter. Ostracods feed chiefly on organic detritus buthave a wide range of diets, including scavenger,carnivoreor herbivore species,some of the latter are spinach lovers in laboratory cultures.

end-ostracotox

Ostracods have various important applications and are mostly known as one of the best palaeoenvironmental indicators. However, in recent years their value as sentinels of anthropogenically induced deteriorations of freshwaters, including different types of pollution, has also beenrecognised.Several laboratory experiments show high sensitivity of various non-marine ostracodspecies to heavy metals, pesticides or herbicides. A 6-day direct contact toxicity test for freshwater sediments (Ostracodtoxkit F manufactured by MicroBioTests Inc.) was even developed and accepted by the International Organisation for Standardization. However, new laboratory bioassays are needed to determine the long-term effects of several emerging pollutants on aquatic wildlife. One of the principal examples of contaminants of emerging concern which are being discovered in freshwaters throughout Europe are endocrine disrupting compounds (EDCs). EDCs are substances that may interfere with the endocrine system and are found in a wide range of products used in everyday life.

Recently, there has been growing interest among the scientific community in testing and learning the potential risk ECDs may pose to freshwater ecosystems. The most highly produced synthetic chemicals in the world with endocrine-disrupting effects are bisphenol A (BPA) used in the production of polycarbonate plastics or epoxy resins, and benzotriazole (BTA) used as a corrosion inhibitor. While a considerable number of studies have been published on BPA and BTA effects in experimental animals and humans, data on long-term toxicity to aquatic invertebrates are scarce. The use of benthic ostracods, which may be exposed to higher BPA and BTA concentrations compared to pelagic species, allows better understanding of the relationship between bioavailability of these potentially hazardous substances and their ecotoxicological effects. Since contaminant-induced stress mechanisms and effects (including decreasing of fitness) are still poorly understood in invertebrates, whole-life-cycle tests are of outermost importance because they cover all sensitive stages and enlarge diversity of endpoints of potential toxicant effects. Suchtests arecurrently one of the major and urgent recommendations of the Organisation for Economic Co-operation and Development.

The present project Monitoring endocrine disruptors in surface waters of central Spain using toxicity and life history ostracod tests (lead by Tadeusz Namiotko) aims at qualifying ecological effects and their application to toxicity testing of BPA and BTAon freshwater ostracods by performing laboratory experiments, including both, short- and long-term toxicity tests. In the short-term acute tests standard values that can be used for determining water quality will be assessed. In the partial- and whole-life-cycle tests several life history traits (hatching success, development time, survival, fecundity) will be monitored via exposure of water containing BPA and BTA at environmentally relevant concentrations. Final results of this study are intended to be used for developing standardized guidelines for testing toxicity of selected EDC on development and reproduction of freshwater ostracods, which eventually could be used as a support monitoring method for environmental risk assessment.

“Plastic is fantastic”

plastic-bottles-860x497

Highly produced synthetic chemicals in the world used in the production of plastics (as e.g. Bisphenol A) have endocrine-disrupting (ED) effects in a variety of organisms, and being released into surface and ground waters, may pose the risk to freshwater ecosystems. Using freshwater ostracods (Ostracoda) to qualify ecological effects of ED compounds seems to be beneficial as these benthic microcrustaceans have been shown to be sensitive to toxic chemicals and compared to planktonic species may allow better understanding of the relationship between bioavailability of potentially hazardous substances and their ecotoxicological effects.

Ostracods are tiny crustaceans that live in most aquatic habitats in all marine and freshwater ecoregions of the world. Their body is protected and completely enclosed by shell formed by two (often strongly calcified) valves, and that is why they are sometimes known as seed shrimps or mussel shrimps. Non-marine species, usually less than 2 mm in size, are essentially benthic or nektobenthic and can be found in a variety of habitats from watering troughs for domestic livestock, pails and other artificial structures, through all kinds of natural permanent and temporary surface waters and various ground waters to thermal springs with water temperature reaching 50°C, damp moss and rainforest leaf litter. Ostracods feed chiefly on organic detritus but have a wide range of diets, including scavenger, carnivore or herbivore species, some of the latter are spinach lovers in laboratory cultures.

Ostracods plates
Scanning electron microscopy images of ostracods (Foto: Tadeusz Namiotko)

Ostracods have various important applications and are mostly known as one of the best palaeoenvironmental indicators. However, in recent years their value as sentinels of anthropogenically induced deteriorations of freshwaters, including different types of pollution, has also been recognised. Several laboratory experiments show high sensitivity of various non-marine ostracod species to heavy metals, pesticides or herbicides. A 6-day direct contact toxicity test for freshwater sediments (Ostracodtoxkit F manufactured by MicroBioTests Inc.) was even developed and accepted by the International Organisation for Standardization. However, new laboratory bioassays are needed to determine the long-term effects of several emerging pollutants on aquatic wildlife.

One of the principal examples of contaminants of emerging concern which are being discovered in freshwaters throughout Europe are endocrine disrupting compounds (EDCs). EDCs are substances that may interfere with the endocrine system and are found in a wide range of products used in everyday life. Recently, there has been growing interest among the scientific community in testing and learning the potential risk ECDs may pose to freshwater ecosystems. The most highly produced synthetic chemicals in the world with endocrine-disrupting effects are bisphenol A (BPA) used in the production of polycarbonate plastics or epoxy resins, and benzotriazole (BTA) used as a corrosion inhibitor. While a considerable number of studies have been published on BPA and BTA effects in experimental animals and humans, data on long-term toxicity to aquatic invertebrates are scarce.

The use of benthic ostracods, which may be exposed to higher BPA and BTA concentrations compared to pelagic species, allows better understanding of the relationship between bioavailability of these potentially hazardous substances and their ecotoxicological effects. Since contaminant-induced stress mechanisms and effects (including decreasing of fitness) are still poorly understood in invertebrates, whole-life-cycle tests are of outermost importance because they cover all sensitive stages and enlarge diversity of endpoints of potential toxicant effects. Such tests are currently one of the major and urgent recommendations of the Organisation for Economic Co-operation and Development.

The project Monitoring endocrine disruptors in surface waters of central Spain using toxicity and life history ostracod tests of IMDEA Water (within the Groundwater Ecology Group) aims at qualifying ecological effects and their application to toxicity testing of BPA and BTA on freshwater ostracods by performing laboratory experiments, including both, short- and long-term toxicity tests. In the short-term acute tests standard values that can be used for determining water quality will be assessed. In the partial- and whole-life-cycle tests several life history traits (hatching success, development time, survival, fecundity) will be monitored via exposure of water containing BPA and BTA at environmentally relevant concentrations. Final results of this study are intended to be used for developing standardized guidelines for testing toxicity of selected EDC on development and reproduction of freshwater ostracods, which eventually could be used as a support monitoring method for environmental risk assessment.

Disentagling the carbon distribution in karst aquifers: the significance for vertical extent of groundwater biota (Carbon-KARST)

postojna-cave-brilliant

Postojna Cave, Slovenia

Aquifers are generally perceived as food-limited ecosystems as they are devoid of phototrophic primary production. This is reflected in a low concentration of organic carbon, that togheter with the reducing of nutrients and oxygen cause a decline of favorable conditions for subterranean life with depth. Consequently, the groundwater biota follows a vertical spatial distribution associated with the availability of nutrients. The true food-limitation of aquifers is currently largely questioned, since the diversity of biota has been documented to be high in several aquifers. Food resources rich underground from the soil bellow the litter zone in forested areas by water percolating trough fissures and creates oligotrophic conditions favouring the development of a rich subterranean populations. Carbon-KARST project aims to determine the relation among the concentration of organic carbon from shallow and deep subterranean habitats and the spatial distribution of groundwater communities in two karst aquifers from Kalkalpen, Austria and Postojna area, Slovenia.

Carbon-KARST will be performed at two eLTER sites, Postojna Cave in Slovenia working in collaboration with Tanja Pipan from Karst Research Institute, Postojna, Slovenia and in Kalkalpen National Park in Upper Austria, in collaboration with Thomas Thomas Dirnböck from Umweltbundesamt, Austria).

NP_NationalparkKalkalpen_LT
Kalkalpen National Park, Austria

The project Carbon-KARST is financed by eLTER H2020 program, an EC-funded project (GA: 654359 – H2020 INFRAIA call 2014-2015).

Groundwater Copepoda (Cyclopoida: Harpacticoida) and Ostracoda in Romania: an evolutionary perspective

Karst landscape in Romania. The Romanian karst ocupy almost 2% of the country and is well developed in the Southern and Western Carpathians. The most important karst areas are located in the Apuseni Mountains (in northwestern Romania), the Banat Mountains (in southwest, adjacent to the border with Serbia) and Dobrogea (in southeast Romania, between the Danube and the Black Sea) (Fig. 1).

Figure 1 (600 dpi)Groundwater crustaceans diversity. The highest diversity among crustaceans in Romanian groundwater is found in the copepods (class: Copepoda; order: Cyclopoida and Harpacticoida) and ostracods (class: Ostracoda; order: Podocopida), represented by more than 160 species and subspecies.

Figure 1. Distribution of copepods and ostracods species in groundwater of Romania in relation to karst landscape  (up) and current vegetation (down).

We analyzed data from 233 georeferenced records for 164 species of groundwater copepods and ostracods from Romania and used a comparative approach to recognize the determinants of the regional-scale richness, endemism, and distribution patterns, with a primary focus on species from the Carpathian Mountains. In addition, we examined the driving forces for the observed pattern of distribution and richness linked to contemporary (groundwater habitat fragmentation and heterogeneity, climate, vegetation) and historical (past climate and vegetation) environmental conditions.

Figure 3 (800dpi)Our analyses showed that: (1) species richness was high, irrespective of habitat heterogeneity, in karst and non-karst areas; (2) the main driver accounting for high species richness in the karst landscape was the rainfall regime (> 1350 mm per year), whereas, in non-karst areas, it was woodland vegetation; and (3) there was significant species richness and richness of phyletic lineages in hypothetical forest glacial refugia of the Carpathian arc. The combination of the distribution pattern, diversification, and evolution of stygobite lineages provides reliable evidence for species persistence in the Romanian groundwater during Pleistocene. It is assumed that the south-eastern Europe and especially the Romanian Carpathians were important regions for surface and underground invertebrates survival during glacial periods and acted as a source of post-glacial colonization processes.

ADDITIONAL KEYWORDS: Carpathian Mountains – endemism – forest – glacial refugia – karst fragmentation – palaeoclimate – Pleistocene – vegetation cover.

© 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2016, 119, 593608 (http://onlinelibrary.wiley.com/wol1/doi/10.1111/bij.12686/abstract)

Groundwater ecosystem services & agriculture: an ecological approach towards the sustainable use of groundwater resources

Article by Anna Sundberg, former researcher at the IMDEA Water Institute

irrigation

Groundwater ecosystem services from groundwater organisms. Groundwater holds unique properties as it provides water of sufficient quality for drinking, to a high extent due to the ecosystem services provided by the groundwater organisms. The ecosystem services provided by organisms are for example purification of water by removal of contaminants, pathogens and virus whereas aquifers functions as water storage and contribute to base flow for rivers and wetlands 5. Groundwater also plays a significant part in the cycling of carbon and other nutrients, which is influenced by the regional climate.

A part of the water purification process is due to physiochemical processes of the soil and the geological formations, but the largest part is due to the complex connections of ecological community in the aquifers. Groundwater ecosystems are relying on energy from the surface, and are thereby allochthonous, because the lack of sunlight prohibits photosynthesis, and the capability of producing energy. Microbial functions performed by bacteria are breakdown of several contaminants infiltrating into the groundwater from the surface. The groundwater microbial community lives mainly in biofilm covering the surface of soil particles and, constitutes an important food source for larger invertebrates organisms, specially crustaceans, that forms the stygofauna6. These organisms live their whole life in groundwater, and are thereby also an important trophic link in subterranean ecosystems. Adversely, larger organisms support the microbial community by burrowing and turning the sediment and thus enhancing water flow in the aquifers, which further provides oxygen and available nutrients for the microbes. Furthermore, the grazing of stygofauna also provides available surface on the soil particles and provide a space and a food source of the microbes7. Thus the groundwater fauna together with the microbes create an ecosystem that provide important functions for water purification water and makes the water suitable for human usage. It is therefore very important to develop sustainable management strategies as to not damage the groundwater fauna and their habitat in order to maintain and provide sustainable water resources for the future.

cropped-portal-1-a.jpg

Examples of groundwater crustacean species

Major factors influencing the groundwater ecosystem Groundwater ecosystems are viewed as a very stable environment with few environmental fluctuations due to the slow response to changes on the surface, however there are several factors affecting the groundwater8. The geological history plays a significant role in the shaping the groundwater communities, as it constitutes the soil and the bedrock, which in turn highly determine the chemical properties of the water but also the depth of the aquifer. The soil composition plays an important role in determining which species at what location and at what time, as the species live in the voids, spaces in between grains. The pore size in turn affects the flow of water within the aquifer that further alters the oxygen and organic content input from the surface which is transported with the water flow underground9.

Potential implications of agriculture on groundwater ecosystems In the Mediterranean area, a large part of the available groundwater resources are used in agriculture, mainly for irrigation during summer. The aquifers are recharged during the rainy seasons in spring and autumn10. Agriculture has a wide range of impacts for the groundwater ecosystem communities; one of the most investigated is the water contamination due to intensive use of fertilizers and pesticides. Fertilizers are used for enhancing the growth of the crops while pesticides and insecticides are used to eliminate pathogens or insects that might attack the crop and thereby minimize the yield. These substances are later percolated down in the groundwater or during the artificially aquifer recharge by irrigation. In high concentrations these compounds might be toxic to organisms or in lower concentrations might case impact on the life history of the organisms by for example affecting the reproduction or feeding behaviors which in turn have negative effects on the survival of the populations and their resilience and resistance11.

Irrigation is important for effective agriculture, as water in many cases is the limiting factor for growth in warmer climates regions. In Spain, 75 % of the abstracted groundwater is used in agriculture, which means that the impact on the groundwater ecosystems in the region is severe. During irrigation a large amount of water are pumped from the aquifer during a relatively short time frame resulting in large quantities of water removals and high fluctuations of the water table in the aquifer. Some organisms will probably be pumped up immediately, but due to the change and rapid fluctuations in water level some organisms might also be stranded in the voids, if they cannot move fast enough to avoid the disturbance12. Even if not all species disappear it might case major disturbances for the whole community, it also has a negative impact on the ability of the populations and lately of the whole ecosystem to recover from disturbances. There is evidence that with water level fluctuations the groundwater habitats suffer from a long term disruption resulting in species loss due to loss of habitat, both for the microbial community and the stygofauna, which means that they cannot carry out their functions of water purification11. Consequently the intensive usage of water in agriculture or for drinking and sanitation is compromised both on short and mid-term time frames.

IMDEA Agua is involved in a number of projects among to secure the groundwater resources for the future and to apply the groundwater ecological assessments in aquifers management. Groundwater Ecology group is investigating the groundwater biotic community’s ecological properties to gain more knowledge in the ecosystem services they provide for groundwater and/or groundwater dependent ecosystems (i.e. hyporheic zone of rivers, wetlands). Within the Smart-Hydro project (RTC-2014-2367-5) the IMDEA Agua Groundwater Ecology group is developing management practices to help farmers to achieve an optimized use of aquifers but also to safeguard the equilibrium among the water use, mainly abstraction for irrigation, and environmental stability for the groundwater biota while securing groundwater resources for the future. We specifically aim to assess the ecosystem services provided by the groundwater invertebrate communities, mainly crustaceans, to detect the impacts of overexploitation and artificial alluvial aquifer recharge on the groundwater ecosystem integrity.

References 

1 Wada, Y. et al. Global depletion of groundwater resources. Geophysical Research Letters 37, n/a-n/a, doi:10.1029/2010gl044571 (2010).

2 Griebler, C. & Avramov, M. Groundwater ecosystem services: a review. Freshwater Science 34, 355-367, doi:10.1086/679903 (2015).

3 Changming, L., Jingjie, Y. & Kendy, E. Groundwater Exploitation and Its Impact on the Environment in the North China Plain. Water International 26, 265-272, doi:10.1080/02508060108686913 (2001).

4 Kløve, B. et al. Climate change impacts on groundwater and dependent ecosystems. Journal of Hydrology 518, 250-266, doi:10.1016/j.jhydrol.2013.06.037 (2014).

5 Schmidt, S. I. & Hahn, H. J. What is groundwater and what does this mean to fauna? – An opinion.Limnologica – Ecology and Management of Inland Waters 42, 1-6, doi:10.1016/j.limno.2011.08.002 (2012).

6 Hancock, P. J., Boulton, A. J. & Humphreys, W. F. Aquifers and hyporheic zones: Towards an ecological understanding of groundwater. Hydrogeology Journal 13, 98-111, doi:10.1007/s10040-004-0421-6 (2005).

7 Boulton, A. J., Fenwick, G. D., Hancock, P. J. & Harvey, M. S. Biodiversity, functional roles and ecosystem services of groundwater invertebrates. Invertebr Syst 22, 103-116, doi:10.1071/Is07024 (2008).

8 Korbel, K. L. & Hose, G. C. Habitat, water quality, seasonality, or site? Identifying environmental correlates of the distribution of groundwater biota. Freshwater Science 34, 329-343, doi:10.1086/680038 (2015).

9 Dole-Olivier, M.-J., Malard, F., Martin, D., LefÉBure, T. & Gibert, J. Relationships between environmental variables and groundwater biodiversity at the regional scale. Freshwater Biology 54, 797-813, doi:10.1111/j.1365-2427.2009.02184.x (2009).

10 Molina, J. L. et al. Aquifers Overexploitation in SE Spain: A Proposal for the Integrated Analysis of Water Management. Water Resources Management 23, 2737-2760, doi:10.1007/s11269-009-9406-5 (2009).

11 Di Lorenzo, T. & Galassi, D. M. P. Agricultural impact on Mediterranean alluvial aquifers: do groundwater communities respond? Fundamental and Applied Limnology / Archiv für Hydrobiologie 182, 271-282, doi:10.1127/1863-9135/2013/0398 (2013).

12 Stumpp, C. & Hose, G. C. The impact of water table drawdown and drying on subterranean aquatic fauna in in-vitro experiments. PLoS One 8, e78502, doi:10.1371/journal.pone.0078502 (2013).

La zona hiporreica en la región mediterránea (Península Ibérica): importancia ecológica y su integración en la gestión hídrica

http://www.madrimasd.org/blogs/remtavares/2016/10/10/132822#more-132822

Rubén Rasines Ladero, IMDEA-Agua, Grupo de Ecología de las Aguas Subterráneas 

Las regiones mediterráneas, entre las que se encuentra gran parte del territorio de la península ibérica (Figura 1a), se caracterizan por una marcada diferenciación entre las estaciones de invierno (periodo húmedo y frío) y verano (periodo seco y cálido). Debido a estas variaciones, la mayor parte de los cursos fluviales de la península ibérica presentan caudales elevados en otoño, asociados a fenómenos de avenida; y cauces con caudales bajos (incluso secos) durante el periodo estival (sequía) [1]. Además, estas regiones se caracterizan por soportar una intensa actividad antrópica que genera diferentes impactos y que condiciona, no solo las características ambientales de los ecosistemas acuáticos superficiales (fenómenos de contaminación, eutrofización, variaciones en caudales), sino también  la de los ecosistemas acuáticos con los que éstos se relacionan [2]. Entre éstos ambientes, destaca la zona hiporreica o ecotono hiporreico (Figura 1b).

La zona hiporreica, entendida como un hábitat para la fauna, fue descrita por primera vez por Pierre-Alfred Chappuis hace 50 años, tras haber realizado muestreos muy intensos en los sedimentos de los ríos de las Montañas Apuseni (noroeste de Rumania) [1]. Chappuis describió este nuevo hábitat acuático como “una corriente de agua subsuperficial por debajo del cauce del río” basándose, sobre todo, en las observaciones respecto a las variaciones que presentaba la fauna acuática presente en estos ambientes [1]. No obstante, este ambiente fue descrito y estudiado en profundidad por el investigador rumano Traian Orghidan. Sus investigaciones supusieron el punto de partida para numerosos investigadores, quienes, a lo largo de los años, han continuado y contribuido al progreso respecto a la comprensión del papel funcional de este compartimento situado en la interfase entre las aguas superficiales y subterráneas [2].

Hoy la zona hiporréica se define como una zona de transición (ecotono) localizada en los sedimentos del lecho de los ríos en la que convergen y se producen intercambios entre las aguas de origen superficial y subterráneo [2]. Su estudio ha evolucionado a lo largo de los años, apareciendo definiciones con un enfoque más hidrológico o hidroquímico; y, a partir de los años 90, más ecológico. No obstante, y a pesar de las diferentes definiciones realizadas, todas ellas ponen de manifiesto la importancia de este ecotono respecto al mantenimiento de la funcionalidad e integridad de los ecosistemas acuáticos con los que se relaciona (ríos, humedales) debido a que este ecotono es el soporte en el que se producen los intercambios de agua, energía, nutrientes y organismos entre el ambiente acuático superficial (río) y el subterráneo (acuífero) [3].

Figura 1. a) Mapa de distribución de las áreas con clima mediterráneo (imagen de dominio público); b) Esquema de la zona hiporreica mostrando la dinámica de flujos de agua que soporta (Fuente:Sandoval Montes, Ismael del Carmen y Rodríguez Rocha, José. 2012. “Evidencias de interacción entre aguas superficiales y subterráneas a través de las zonas hiporreicas mediante el uso de la hidroquímica y el análisis multivariado en el acuífero de Cuajinicuilapa, Guerrero, México“. International Journal of statistics and geography. 3(2): 116-129).

En la región mediterránea, debido a que las condiciones ambientales (temperatura, precipitación, caudales, etc.) son más variables, y las presiones antrópicas presentan una intensidad creciente, las funciones y servicios ambientales generados en la zona hiporreica adquieren una gran relevancia, especialmente ante los fenómenos de avenida y/o sequía, así como ante variaciones de caudal producidos por sobre-explotación de agua para el riego y/o embalsamientos de agua en los cauces, que provocan una modificación en las interacciones entre el ambiente acuático superficial y subterráneo (Figura 2). En este sentido, las características más relevantes del ambiente hiporreico en las regiones mediterráneas responden a: i) su capacidad de actuar como filtro ante la introducción de sustancias tóxicas hacia el medio subterráneo (acuíferos); ii) su capacidad de servir como refugio para la fauna, especialmente cuando las condiciones en el ambiente superficial y/o subterráneo no son adecuadas para permitir el establecimiento y/o el mantenimiento de sus poblaciones [4]. Además, también aparecen otras características inherentes al propio ecotono hiporreico mediterráneo, como son: iii) su capacidad de albergar una gran diversidad de organismos (la región Mediterránea está considerada como uno de los 25 puntos calientes de biodiversidad global) [5]. La región mediterránea es una de las más vulnerables ante los fenómenos asociados al cambio climático, de modo que las capacidades del ecotono hiporreico de actuar como zona de refugio para la fauna bentónica, zona de recolonización del ambiente superficial y/o subterráneo, filtro ante contaminación y/o como reservorio de nutrientes, podrían verse comprometidos en un futuro [3,6].Figura 2. Diferente situaciones indicando conexión entre un río y un acuífero a través de la zona hiporreica: a) río que recarga a un sistema acuífero; b) río que infiltra agua a un sistema acuífero desconectado a través de la zona hiporreica (zona de descarga); c) río que recibe aporte de aguas subterráneas (zona de recarga/surgencia). (Fuente: Arumí, J.L.; Rivera, Diego; Muñoz, Enrique; y Billib, M. 2012. “Interacciones entre el agua superficial y subterránea en la región del Bío Bío de Chile“. Obras y proyectos. 12: 4-13).

hyporheic-ruben-1

Figura 3. Diferente situaciones indicando conexión entre un río y un acuífero a través de la zona hiporreica: a) río que recarga a un sistema acuífero; b) río que infiltra agua a un sistema acuífero desconectado a través de la zona hiporreica (zona de descarga); c) río que recibe aporte de aguas subterráneas (zona de recarga/surgencia).

(Fuente: Arumí, J.L.; Rivera, Diego; Muñoz, Enrique; y Billib, M. 2012. “Interacciones entre el agua superficial y subterránea en la región del Bío Bío de Chile“. Obras y proyectos. 12: 4-13).

En España, los estudios respecto a la zona hiporreica son escasos. Los primeros datan del año 1978 y se centraron en la descripción de la fauna presente en ríos de la zona del Levante (sureste de España) [7]. Los estudios siguientes se centraron en la caracterización respecto a la dinámica de nutrientes y su importancia como almacenamiento transitorio; mientras que, en los últimos años, también se ha considerado la inclusión de este ecotono en los procesos de restauración fluvial [8]. No obstante, en España, el principal impulso respecto al conocimiento del ambiente hiporreico y su fauna, se ha producido recientemente, sobre todo a partir de estudios realizados en ríos de la Comunidad de Madrid, y de la Comunidad Valenciana. Estos estudios están encaminados a realizar una caracterización de las condiciones ambientales (hidroquímicas, geológicas, estructura de los sedimentos que conforman el lecho fluvial, etc.) y su relación con las comunidades faunísticas que aparecen en él[9,10,11]. A pesar de que en los últimos años se ha producido un incremento respecto al conocimiento de las características, funciones, dinámicas, fauna y servicios ambientales presentes o generados en el ambiente hiporreico, tanto a nivel nacional como global, existen aún ciertos aspectos en los que se requiere seguir investigando [12,13]. Entre estos aspectos se encuentran: i) la determinación de la importancia de los procesos físicos respecto a la funcionalidad del ecotono hiporreico; ii) el papel de los organismos invertebrados y de las comunidades microbianas en los procesos hiporreicos; iii) la importancia de la zona hiporreica y su biota en el metabolismo global del ecosistema fluvial; iv) la contribución de la fauna hiporréica en la degradación de distintos contaminantes; y v) la necesidad de permitir una mayor accesibilidad a los resultados científicos que permitan el desarrollo de legislación y medidas para el manejo, la protección y la restauración de este ecotono [14].

Pese al conocimiento sobre el ambiente hiporreico, y la vulnerabilidad que éste tiene ante fenómenos de contaminación, variabilidad climática, etc., en la actualidad no se contempla su protección desde un punto de vista legislativo (ni global, ni europeo, ni nacional), ni se integra dentro de la legislación vigente referente a otros ecosistemas acuáticos como los superficiales y/o subterráneos. Por este motivo, y a pesar de la aprobación de la Directiva Marco del Agua (2000/60/CE), en la que se ha establecido un marco legal respecto a la caracterización y protección de las aguas superficiales, incluyendo aspectos relacionados con las aguas subterráneas, aún es necesario implementar e incluir otros elementos, como el ecotono hiporreico, para conseguir una caracterización, protección y gestión integrada de todos los elementos que conforman los ecosistemas acuáticos continentales.

Desde el instituto IMDEA-Agua, el grupo de Ecología de Aguas Subterráneas, dirigido por la Dra. Iepure, se están llevando a cabo las investigaciones necesarias para caracterizar el ambiente hiporreico asociado a diferentes ríos de la Comunidad de Madrid (cuenca del Jarama) desde un punto de vista ecológico (función y procesos ecosistémicos, servicios ambientales, etc.) y, sobre todo, faunístico (centrando sus investigaciones en el grupo de los microcrustáceos: ostrácodos y copépodos). Para ello utilizan, entre otras técnicas, métodos no invasivos basados en técnicas geofísicas como la tomografía de resistividad eléctrica (ERT, según sus siglas en ingles) que permiten caracterizar la estructura interna de los sedimentos que conforman el ecotono hiporreico, así como determinar su tamaño y el grado de conectividad con el río, e incluso con el acuífero aluvial en la vertical y en la horizontal. Estas investigaciones podrían suponer, no solo una mejora en la comprensión de todos los aspectos relacionados con la zona hiporreica desarrollada en ambientes mediterráneos, sino el establecimiento de una base científica que permita el desarrollo de una legislación que integre todos los componentes asociados a los ecosistemas acuáticos continentales (superficiales – hiporreico – subterráneos).(Más información en:http://www.agua.imdea.org/investigacion/proyectos-de-investigacion/ecologia-aguas-subterraneas).

Figura 3. De izquierda a derecha: transecto seleccionado para la realización del perfil eléctrico mediante la técnica de tomografía de resistividad eléctrica (ERT); instalación de los electrodos en el lecho del río para la medición de la resistividad eléctrica y determinación del tamaño del ecotono hiporreico en un punto del río Henares; organismo (copépodo: ciclopoide) encontrado en el ambiente hiporreico; organismo (ostrácodo) identificado en el ambiente hiporreico.

Bibliografía

[1] Chappuis, P. A. 1942. “Eine neue Methode zur Untersuchung der Grundwasser-fauna”. Acta Sci. Math. Nat. Kolozsvar. 6: 3-7.

[2] Orghidan, T. 2010. “A new habitat of subsurface waters: the hyporheic biotope”.Fundamental and Applied Limnology / Archiv für Hydrobiologie. 176(4): 291-302.

[3] Boulton, A.J.; Datry, T.; Kasahara, T.; Mutz, M.; y Stanford, J.A. 2010. “Ecology and management of the hyporheic zone: stream–groundwater interactions of running waters and their floodplains”. Journal of the North American Benthological Society. 29(1): 26-40.

[4] Dole-Olivier, M-J. 2011. “The hyporheic refuge hypothesis reconsidered: A review of hydrological aspects”. Marine and Freshwater Research. 62(11): 1281-1302.

[5] Mellado Díaz, A; Suárez Alonso, M.L.; Vidal-Abarca Gutiérrez, M.R. 2008.“Biological traits of stream macroinvertebrates from a semi-arid catchment: patterns along complex environmental gradients”. Freshwater Biology. 53: 1-21.

[6] Argerich, A; Martí, E.; Sabater, F.; Ribot, M.; von Schiller, D.; Riera, J.L. 2008.“Combined effects of leaf litter inputs and a flood on nutrient retention in a Mediterranean mountain stream during fall”. Limnology and Oceanography. 53(2): 631-641.

[7] Henry, J.P. y Magniez, G. 1978. “1st hyporheic Proasellus from Spain – Proasellus – Jaloniacus -n-sp (Crustacea, Isopoda, Asellota)”. International Journal of Speleology. 9(2): 125-130.

[8] Benda, L.; Miller, D.; Barquín, J. 2011. “Creating a catchment scale perspective for river restoration”. Hydrology and Earth System Sciences. 15(9): 2995-3015.

[9] Iepure, S.; Meffe, R.; Carreño, F.; Rasines-Ladero, R.; de Bustamante, I. 2014. “Geochemical, geological and hydrological influence on ostracod assemblages distribution in the hyporheic zone of two Mediterranean rivers in central Spain”.International Review of Hydrobiology. 99(6): 435-449.

[10] Rasines-Ladero, R. y Iepure, S. 2016. “Parent lithology and organic matter in fl uence the hyporheic biota of two Mediterranean rivers in central Spain”. Limnetica. 35(1): 19-36.

[11] Mezquita, F.; Hernández, R.; Rueda, J. 1999. “Ecology and distribution of ostracods in a polluted Mediterranean river”. Palaeogeography, Palaeoclimatology, Palaeoecology. .148: 87-103.

[12] Mugnai, R; Messana, G; di Lorenzo, T. 2015. “The hyporheic zone and its functions: Revision and research status in Neotropical regions”. Brazilian Journal of Biology. 75(3): 524-534.

[13] Blondel, J.; Aronson, J.; Bodiou, J.Y.; Boeuf, G. 2010. The Mediterranean Region. Biological Diversity in Space and Time. Ed(s): Oxford University Press: Nueva York.

[14] Marmonier, P.; Archambaud, G.; Belaidi, N.; Bougon, N.; Breil, P.; Chauvet, E.; Claret, C.; Cornut, J.; Datry, T.; Dole-Olivier, M.-J.; Dumont, B.; Flipo, N.; Foulquier, A.; Gérino, M.; Guilpart, A.; Julien, F.; Maazouzi, C.; Martin, D.; Mermillod-Blondin, F.; Montuelle, B.; Namour, Ph.; Navel, S.; Ombredane, D.; Pelte, T.; Piscart, C.; Pusch, M.; Stroffek, S.; Robertson, A.; Sanchez-Pérez, J.-M.; Sauvage, S.; Taleb, A.; Wantzen, M.; Vervier, Ph. 2012. “The role of organisms in hyporheic processes: gaps in current knowledge, needs for future research and applications”. Annales de Limnologie – International Journal of Limnology. 48: 253-266.